This project is a continuation of an ongoing investigation of the period of declining female reproductive function, using female golden hamsters. We are assaying steroid hormone receptors in uteri of intact or ovariectomized, estrogen primed animals or controls at various ages. For correlation with the receptor studies, autoradiographic localization of 3H-steroids in uteri is also being performed. Histochemical analyses of enzymes, glycosaminoglycans and glycogen in the uteri is being carried out. Ovarian function is being assayed by histochemical studies and measurements of steroid levels in the circulation. Assays for gonadotrophins are also being done in animals of various ages. All hormone measurements are based on established radioimmunoassay procedures.